Poseidon Linux is a distribution developed and maintained by a number of scientists at Rio Grande Federal University, for scientific and academic use, basing itself on Ubuntu (formerly Kurumin before Kurumin disappeared). Version 3.1 is old news now, but it is the version I had handy.
The default Poseidon desktop. It looks very similar to Ubuntu of the time, just with a blue theme applied.
The Poseidon about page, which defaults to Portuguese every time you open it.
2732 days! That's a long time. :P
The updater is no different from regular Ubuntu.
The Poseidon menu is laid out identical to Ubuntu, but with an extra "Poseidon" entry that contains all the scientific stuff.
It appears as though the theme wasn't saved. Oh well, I guess if you change it you aren't going back without some frustration.